pipe

Opens a pair of connected pipes like the corresponding system call.
Note that if you set up a loop of piped processes, deadlock can occur
unless you are very careful. In addition, note that Perl's pipes use
IO buffering, so you may need to set $
to flush your WRITEHANDLE after each command, depending on the
application.

On systems that support a close-on-exec flag on files, that flag is set
on all newly opened file descriptors whose
filenos are higher than the current value of
$^F (by default 2 for STDERR
). See $^F in perlvar.